In recent years, with the process of globalization, the international competition of manufacturing industry has become increasingly fierce. In order to remain invincible in the competition, many enterprises are committed to the research of various topics such as "reducing cost", "shortening delivery time", and "improving quality". Especially in the recent re understanding of "Made in Japan", the high-precision and efficient processing of molds has become an important keyword. In other words, the role of cutting tools, which are indispensable tools in mold processing, has now been considered to be a crucial factor.

In recent years, the needs of users who use cutting tools have also changed. In the past, people generally believed that tools were consumables, so they wanted to reduce the cost of tools by reducing the use. Recently, people's views have changed, and they believe that the processing cost should be reduced by giving full play to the role of tools. This is exactly the view of "halving the processing" put forward by Hitachi Tools 4 years ago. In order to meet the changing needs of users, it is necessary for tool manufacturers to focus on developing more efficient tools.

1. Solid carbide end mill "Epoch Deep Radius"

(1) Machinability

In recent years, the trend of replacing the former EDM with cutting is becoming more and more obvious, and this demand gradually turns to cutting the narrow and deep parts of the workpiece. When the end mill is used for deep cutting such narrow and deep parts, the mainstream tool applicable is the small diameter ball end mill (Hitachi Tools is also producing the Epoch deep cutting ball end mill and the Epoch pen deep cutting ball end mill series). However, when using small diameter ball end milling cutter for high efficient deep cutting, the following problems will occur (i.e., the problems existing in replacing EDM with cutting): ① cutting resistance is easy to increase; ② It is difficult to improve the cutting speed at the center (the top center edge is easy to be damaged); ③ There is a theoretical cutting residue (the radial cutting amount of the tool cannot be too large).

To solve the above problems, Hitachi Tools has developed a small diameter long neck series Epoch deep fillet end mill. When using a small diameter end mill for deep cutting, if the cutting resistance at the front end of the cutting edge of the tool is too large, it will produce vibration and cannot be processed under efficient cutting conditions, thus affecting the processing efficiency. From the angle of cutting resistance, the comparison between ball end milling cutter and R angle end milling cutter shows that the contact area of the cutting edge of the latter is small, and the cutting resistance is relatively small.

In addition, when cutting contours, ball end milling cutter has theoretical cutting residues, especially the end transverse edge with low cutting speed is easy to be damaged. The fillet end milling cutter can usually form a certain cutting surface, so it has the advantage of stable and reliable processing. The Epoch deep fillet end mill developed now can prevent chatter during deep cutting. In order to further improve the processing efficiency, the inverted cone design is adopted. This design can prevent the peripheral edge from contacting the material to be cut due to the bending of the tool during the cutting process, so as to achieve stable machining. In addition, the tool coating adopts TH (TiSiN) hard coating with high hardness, high heat resistance and wear resistance, which is very suitable for direct deep cutting of high hardness materials.

The following describes the characteristics of Epoch deep fillet end mill through machining examples.

(2) Machining example

① Examples of efficient groove machining

In order to process grooves efficiently, it is necessary to increase the step distance in XY direction to a certain extent. However, if ball end milling cutter is used for processing, the center edge that cannot improve the cutting speed will bear a great load and have to reduce the cutting conditions.

From the results of groove processing with ball end milling cutter, it can be seen that if the set XY step distance is increased, the damage degree of the central edge will also increase; If the set XY step is reduced and the cutting conditions are reduced, the wear of the front central cross edge is increased, although no damage to the central edge is observed. From the results of using Epoch deep fillet end milling cutter to process grooves, it can be seen that not only the cutting is stable, but also the wear is reduced, and the groove processing effect of high hardness (about 50HRC) hot die forging steel workpiece is good.

In this processing example, compared with the ball end milling cutter, the processing time required by the new fillet end milling cutter is shortened by about 1/4, and the processing cost is reduced by more than half.

② Deep Cutting of High Hardness Materials

The results of machining SKD11 cold working die steel (60HRC) with a long neck end mill show that the peripheral cutting edge of the ball end mill is very damaged; However, the Epoch deep processing fillet end milling cutter is not damaged, only uniformly worn. It can be inferred that because the contact length of the cutting edge of the ball end mill is large, the cutting resistance is also large, and the peripheral cutting edge with high cutting speed is easy to be damaged. This is the same as Example ①, and the fillet end milling cutter has obvious advantages.

It can be seen from the comparison between the round end milling cutter of Hitachi Tools and the round end milling cutter of other companies under the same processing conditions that the round end milling cutter produced by other companies does not use the inverted cone design, so the processing effect of the high hardness materials over 60HRC is not ideal. The new generation of deep cutting fillet end mill of Hitachi Tools adopts the unique design of anticlinal shape, and the peripheral cutting edge is point contact cutting. Even when the straight cutting method is used to process high hardness materials, the cutting resistance is very small, and the processing state is stable.

It can be seen from the processing example of Epoch deep fillet end milling cutter that the cutter has excellent performance, especially for deep cutting of high hardness materials. In a word, to give full play to the role of the fillet end milling cutter, the materials that have been heat treated and quenched can be directly grooved. As the processing process is shortened, the processing cost can be greatly reduced. The experiment shows that the machining efficiency can be improved by more than 5 times and the machining cost can be reduced by 35% by using the round end milling cutter.

2. Indexable fillet end mill for large feed rough machining

(1) Multi edge large feed fillet end mill

The mold industry generally adopts the cutting mode of small cutting depth and large feed to achieve efficient processing, but the market demand requires further improvement of processing efficiency. To meet this need, Hitachi Tools has developed multi cutting edge tools and coatings that can also withstand high cutting speeds under high feed conditions. The design concept of multi edge large feed round corner cutter is to reduce the cutting edge size without reducing the edge strength within the limited tool outer diameter according to the previous edge number design method. Set the main cutting edge radius of the large feed fillet end milling cutter to R8. Compared with the round blade with the same radius of R8, it has the same edge strength, but minimizes the blade area, thus realizing multi cutting. Previous OD was φ 32 are all 2 blades, while the number of blades of multi blade large feed fillet end milling cutter is up to 5, which is 2.5 times higher than that of previous products.

(2) Features of large feed tool

Previously, indexable cutters used for rough machining were generally equipped with round inserts. On the surface, it seems that a large amount of cutting depth can be obtained, and a large amount of materials can be cut at a time. However, because the contact length between the cutting edge and the material to be machined is greater than the contact length of the linear blade, the cutting resistance is increased, and it is difficult to achieve large feed cutting. In addition, the round blade is subject to radial force when the tool overhangs longer, which is easy to cause tool bending and chatter. The cutting edge of the multi edge large feed round corner end mill is designed at the bottom of the tool rotation axis, so the cutting resistance mainly acts on the axial direction, that is, the multi edge large feed round corner end mill is not prone to chatter even if it has a long overhang, and can achieve stable processing. At the same time, by miniaturizing the blade, the length of the cutting edge is significantly shorter than that of the previous large feed tool, and the cutting resistance is reduced, so the cutting force is effectively controlled through multi cutting.

(3) Advantages of small cutting depth and large feed machining

Small cutting depth and large feed machining are the application conditions of large feed cutters, which have the advantages of large material removal rate and high machining efficiency. Compared with high efficiency machining with large cutting depth, high efficiency rapid feed machining can be carried out within the maximum feed limit range of the machine tool workbench when the cutting depth is reduced.

When using a round blade to increase the cutting depth to improve the machining efficiency, there will be obvious cutting residues left on the workpiece after machining, which will increase the processing load of subsequent finishing tools. Although the rough machining efficiency is very high, it will reduce the processing efficiency of subsequent processes. Compared with this, when using small cutting depth and large feed machining, the cutting residue of rough machining is reduced, which is closer to the shape of final finishing, so as to reduce the load of finishing tools in subsequent processes, improve the efficiency of rough machining and finishing at the same time, and realize efficient machining stably and reliably.

3. Super lubricating JX coating

As mentioned above, while improving the blade shape and increasing the number of blades to improve the processing efficiency, if the tool rotation speed can be increased and the cutting speed and feed speed can be accelerated, the processing efficiency can be further improved. However, when the cutting speed is higher than the current cutting speed, the current tool coating is insufficient to withstand the high temperature and pressure generated by cutting. Therefore, we have re recognized the influence of small cutting depth and large feed cutting on the cutting edge, and determined the necessary performance for high-speed: even at high temperature, it has the lubricating performance that can inhibit the friction between chips and tools generated by large feed cutting. Therefore, Hitachi Tools has successfully developed a series of titanium compound coatings with strong lubricity. This new performance JX coating, which can be used for efficient machining, can effectively reduce the wear of the crater and the rear tool surface, and effectively prevent the adhesion of the cutting edge.

(1) JX coating with low friction coefficient, high hardness and high toughness

JX coating adds self-lubricating materials to titanium and aluminum compounds, which can form a thin oxide layer on the coating surface by using cutting heat. The oxide layer can improve the lubrication performance, control the rise of cutting temperature, reduce the affinity between the cutting edge and the workpiece to be machined, and inhibit the adhesion of the cutting edge. The hardness of JX coating is equivalent to that of TiSiN series coating with the highest hardness. The high hardness can prevent cutting edge wear in high-speed and efficient machining environment, and greatly extend the service life of tools. The ceramic hard coating is difficult to effectively prevent hot cracks caused by intermittent cutting, which is unique to milling, but the JX coating has a high resistance to blade breakage due to its greatly improved toughness. It can be seen that JX coating is a new generation of coating with lubricity, wear resistance and anti chipping. On the premise of the same number of blades and service life, the cutting speed of the coating is 40% higher than that of the previous coating.

(2) An Example of High Speed Cutting with Multi blade and Large Feed Fillet End Milling Cutter

Example of efficient machining on the latest CNC machining center machine tool (cutting feed speed up to 50m/min) using a multi edge large feed fillet end mill and JX coated inserts: the external diameter of the cutting edge of the multi edge large feed fillet end mill is φ 32mm, with 5 cutting edges; Blade brand is JX1045; The processed material is 40CrMnMo7 (equivalent to SKT3 of JIS standard). When the cutting speed Vc=300 mm/min, the spindle speed n=3000/min, the cutting feed speed Vf=50 m/min, the feed per tooth fz=3.3 mm/tooth, and the cutting depth ɑ p ×ɑ e=0.3 × Under the cutting condition of 25mm, the cutting can be completed easily. The high-speed CNC machining center used for machining has not been widely used at home and abroad. Compared with the high-speed CNC machining center commonly used at present with a cutting feed rate of 10~20m/min, the machining efficiency can be improved by 2.5~5 times. The new generation of multi edge large feed round corner end milling cutter can maximize the functions of the existing high-speed CNC machine tools.